Question

Two compound samples are found to have the same mass percentages of the same elements. what can you conclude about the two samples

Answer 1

If the samples have the same mass percentage of same elements , it implies that they have the same empirical formula.

An empirical formula is defined as the simplest positive integer ratio of the atoms present in that compound. It does not tell about the total number of atoms present in that compound.

For example- C2H4O and C4H8 O2 have the same empirical formula i.e. C2H4O.

we can also determine the mass percentage of each element as follows:

1) Total mass of C2H4O = (2×12.0 g/mol) + ( 4×1.0 g/mol) + (1× 16.0 g/mol)

= 44 g/mol

Now Mass percentage of C in C2H4O = [ (2×12.0) / (44 g/mol) ]×100

= 54.5 %

Mass percentage of H in C2H4O = [ (4×1.0) / (44 g/mol) ]×100

= 9.1 %

Mass percentage of O in C2H4O = [ (1×16.0) / (44 g/mol) ]×100

= 36.4 %

2) Similarly, Total mass of C4H8O2 = (4×12.0 g/mol) + ( 8×1.0 g/mol) + (2× 16.0 g/mol)

= 88 g/mol

Now Mass percentage of C in C4H8O2 = [ (4×12.0) / (88 g/mol) ]×100

= 54.5 %

Mass percentage of H in C4H8O2 = [ (8×1.0) / (88 g/mol) ]×100

= 9.1 %

Mass percentage of O in C4H8O2 = [ (2×16.0) / (88 g/mol) ]×100

= 36.4 %

∴ It can be seen that in both the compounds with same empirical formula have same mass percentage of each elements.

Thus, we can say that If the samples have the same mass percentage of same elements , it implies that they have the same empirical formula.

Answer 2

This implies that they have the same empirical formula. Because an empirical states a chemical formula showing the simplest ratio of elements in a compound rather than the total number of atoms in the molecule

For example, say they both have an empirical formula of CH2.

One of them may be C8H16 and the other may be C7H14.